Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Head of a vector

  1. Sep 28, 2003 #1
    The question asked me to find the head of a vector [a,b,c] whose length is 3 and is in the same direction as vector

    So I found the follwing:

    Let vector x be the unknown vector


    Since they are both in the same direction, they both must have the same direction angles right?


    Cos alpha = -3/13 which is equal to a/3
    Cos beta = -4/13 which is equal to b/3
    Cos gamma = 12/13 which is equal to c/3

    Then I got the values for a,b and c but the book shows me a different answer. What am I doing wrong here?
  2. jcsd
  3. Sep 28, 2003 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    What values did you get, and what does the book say?
  4. Sep 28, 2003 #3
    I found my answer to be correct because I did a similiar question and found my method to work. Thx though
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook